1. Bluetooth Connection: Bluetooth 4.1 technology ensures strong signal and fast transmission, and offers high-fidelity stereo music. Compatible with iOS / Android Smart phones and other Bluetooth-enabled devices. 2. Hands-free Calls: RS-01 headphone supports hands-free calls with high-grade microphone, thoroughly setting free your hands from answering the call during exercise. 3. Suitable for Sports: In-ear sport headphone is suitable for running, climbing, driving and other outdoor sports. Magnet design makes it easy and convenient to wear on your neck when in no use. 4. Duration Time: Built-in rechargeable 45mAh Lithium battery lasts more than 6 hours of talking time or 4 hours of music playing time and 100 hours of standby time on one full charge. 5: Easy Operation: With three button line control, easily control playing / pausing, volume up and down, answering / ending an incoming-call and redialing the last number.